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    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      const str = "abcdxef";
      console.log(str.includes("c", 3));
      console.log(str.includes("x"));
      console.log(str.includes("abc"));
      console.log(str.includes("abd"));

      console.log("startsWith", str.startsWith("a"));
      console.log("startsWith", str.startsWith("abc"));
      console.log("endsWith", str.endsWith("xef"));
      console.log("endsWith", str.endsWith("f"));

      /* const str = {
        0: "a",
        1: "b",
        2: "c",
        3: "d",
        4: "c"
        5: "e",
        6: "f",
      }; */
    </script>
  </body>
</html>
